Entertaining physics pressure. Review from the Internet about water pressure

And again I will allow myself to touch on old books, this time the two-volume “Entertaining Physics”. The author of this book, remarkable in all respects, is Yakov Isidorovich Perelman, who was the largest and most famous popularizer of science in the USSR.

He is the author of a whole galaxy of popular science books, of which “Entertaining Physics” is just the most famous. It has gone through more than 20 reprints (I can’t say for sure, but if it has been reprinted again recently, it will already be about 30 reprints). This two-volume book was wildly popular in the then Union and would now be called a bestseller.

I wanted to buy it for myself for a long time and I finally got it (this was several years ago, and I was looking for this two-volume book for years). It is written in a very simple and understandable language, and in order to understand this book, the knowledge of the school physics course for grades 7-9 is enough. Moreover, with the help of this book, you can conduct a number of very instructive and serious experiments at home.

Plus, everything else, it examines in detail the most typical mistakes of science fiction writers specializing in science fiction (H.G. Wells and Jules Verne are especially beloved by the author), however, Yakov Isidorovich does not ignore other authors and other works. For example, take the same Mark Twain, who gave the world a lot of satirical works.

Let me just cite one of the paragraphs of this wonderful two-volume book?

"Barometer Soup"

In the book “Wanderings Abroad”, the American humorist Mark Twain talks about one incident of his Alpine travel - an incident, of course, fictitious:

Our troubles are over; therefore, people could relax, and I finally had the opportunity to pay attention to the scientific side of the expedition. First of all, I wanted to determine the altitude of the place where we were using a barometer, but, unfortunately, I did not get any results. From my scientific readings I knew that either a thermometer or a barometer must be boiled to obtain a reading. I didn’t know for sure which of the two, so I decided to boil both.

And yet I didn’t get any results. Having examined both instruments, I saw that they were completely damaged: the barometer had only one copper needle, and a lump of mercury was dangling in the thermometer ball...

I found another barometer; it was completely new and very good. I boiled it for half an hour in a pot of bean soup, which the cook had prepared. The result was unexpected: the instrument stopped working, but the soup acquired such a strong barometer flavor that the head cook - a very smart man - changed its name in the list of dishes. The new dish earned everyone's approval, so I ordered barometer soup to be prepared every day. Of course, the barometer was completely ruined, but I didn’t particularly regret it. Since it didn’t help me determine the height of the area, it means I don’t need it anymore.

Jokes aside, let's try to answer the question: what really should have been “boiled”, a thermometer or a barometer?

Thermometer, and here's why.

From previous experience ( this fragment was removed from the main context, as I mentioned at the very beginning.— approx. mine) we have seen that the lower the pressure on water, the lower its boiling point. Since atmospheric pressure decreases with elevation in the mountains, the boiling point of water should also decrease. Indeed, the following boiling temperatures of pure water are observed at different atmospheric pressures:

In Bern (Switzerland), where the average atmospheric pressure is 713 mm Hg. Art., water in open vessels already boils at 97.5 ° C, and at the top of Mont Blanc, where the barometer shows 424 mm Hg. Art., boiling water has a temperature of only 84.5 ° C. For every kilometer rise, the boiling point of water drops by 3°C. This means that if we measure the temperature at which water boils (as Twain put it, if we “boil the thermometer”), then by consulting the corresponding table, we can find out the height of the place. To do this, you must, of course, have pre-compiled tables at your disposal, which Mark Twain “simply” forgot about.

The instruments used for this purpose - hypsothermometers - are no less convenient to carry than metal barometers, and give much more accurate readings.

Of course, a barometer can also serve to determine the altitude of a place, since it directly, without any “boiling”, shows the pressure of the atmosphere: the higher we rise, the less pressure. But even here, you need either tables showing how air pressure decreases as you rise above sea level, or knowledge of the corresponding formula. All this seemed to get mixed up in the comedian’s head and prompted him to “cook barometer soup.”

I wonder how many of my blog readers knew the answer before the end of the passage? And which of them remembers (knows) this mysterious formula mentioned in an excerpt from the book?

Yes, by the way, thanks to atmospheric pressure you can perform very interesting physical tricks. When I was a physics teacher at school, I showed schoolchildren while studying the topic “atmospheric pressure” a simple trick. He took a glass tube with two open ends, about 50 cm long. With the flattened (narrower) end, he placed the tube in a vessel with water and waited for water to fill the tube. Then he plugged the wider edge of the tube with his thumb, removed the tube from the vessel and turned it over. From the narrow edge of the tube, water flowed to a fairly decent height. Then, quietly replacing the vessel with water, I gave the schoolchildren the opportunity to repeat the trick, but they didn’t succeed. The inevitable “debriefing” began, at which the essence of this trick was revealed.

Have any of you already guessed what the catch was?

P.S. A gypsum thermometer is also known as a thermobarometer. Note that at pressures close to atmospheric, a change in the boiling point of pure water by 0.1 °C corresponds to a change in atmospheric pressure by 2.5-3 mm Hg. Art. (or an equivalent change in terrain height of approximately 30 m). The scale of a modern thermobarometer is divided into hundredths of a degree or the corresponding units of pressure in mmHg. Art. The device, in addition to a thermometer with a scale, includes a boiler - a metal vessel with clean water and a heater. Despite its simplicity, the thermobarometer is a convenient and accurate instrument suitable for use in expeditionary conditions.

What science is rich in interesting facts? Physics! 7th grade is the time when schoolchildren begin to study it. So that a serious subject does not seem so boring, we suggest starting your studies with interesting facts.

Why are there seven colors in the rainbow?

Interesting facts about physics can even involve rainbows! The number of colors in it was determined by Isaac Newton. Aristotle was also interested in such a phenomenon as the rainbow, and Persian scientists discovered its essence back in the 13-14th century. However, we are guided by the description of the rainbow that Newton made in his work "Optics" in 1704. He isolated the colors using a glass prism.

If you look closely at a rainbow, you can see how colors smoothly flow from one to another, forming a huge number of shades. And Newton initially identified only five main ones: violet, blue, green, yellow, red. But the scientist had a passion for numerology, and therefore wanted to bring the number of colors to the mystical number “seven”. He added two more colors to the description of the rainbow - orange and blue. This is how a seven-color rainbow turned out.

Liquid form

Physics is all around us. Interesting facts can surprise us, even when it comes to something as common as ordinary water. We are all accustomed to thinking that a liquid does not have its own shape; even a school physics textbook says this! However, this is not true. The natural shape of a liquid is a sphere.

Height of the Eiffel Tower

What is the exact height of the Eiffel Tower? And it depends on the weather! The fact is that the height of the tower varies by as much as 12 centimeters. This occurs because in hot sunny weather the structure heats up, and the temperature of the beams can reach up to 40 degrees Celsius. And as you know, substances can expand under the influence of high temperature.

Dedicated scientists

Interesting facts about physicists can not only be funny, but also tell about their dedication and devotion to their favorite work. While studying the electric arc, physicist Vasily Petrov removed the top layer of skin on his fingertips to sense weak currents.

And Isaac Newton inserted a probe into his own eye to understand the nature of vision. The scientist believed that we see because light presses on the retina.

Quicksand

Interesting facts about physics can help you understand the properties of such an interesting thing as quicksand. They represent: A person or animal cannot completely sink into quicksand due to its high viscosity, but it is also very difficult to get out of it. To pull your foot out of quicksand, you need to make an effort comparable to lifting a car.

You cannot drown in it, but dehydration, sun, and tides pose a danger to life. If you fall into quicksand, you need to lie on your back and wait for help.

Supersonic speed

You know what the first device was that overcame the Common Shepherd's Whip. The click that scares cows is nothing more than a pop when overcome. When hit hard, the tip of the whip moves so fast that it creates a shock wave in the air. The same thing happens with an airplane flying at supersonic speed.

Photon spheres

Interesting facts about physics and the nature of black holes are such that sometimes it is simply impossible to even imagine the implementation of theoretical calculations. As you know, light consists of photons. When photons fall under the influence of a black hole's gravity, they form arcs, regions where they begin to orbit. Scientists believe that if a person is placed in such a photon sphere, he will be able to see his own back.

Scotch

It is unlikely that you unwound tape in a vacuum, but scientists in their laboratories did it. And they found out that when unwinding, a visible glow and X-ray emission occurs. The power of X-ray radiation is such that it even allows you to take pictures of body parts! But why this happens is a mystery. A similar effect can be observed when asymmetric bonds in a crystal are destroyed. But here's the problem - there is no crystalline structure in the tape. So scientists will have to come up with another explanation. There is no need to be afraid of unwinding the tape at home - no radiation occurs in the air.

Experiments on humans

In 1746, the French physicist and part-time priest Jean-Antoine Nollet investigated the nature of electric current. The scientist decided to find out what the speed of electric current is. Here's how to do it in a monastery...

The physicist invited 200 monks to the experiment, connected them using iron wires and discharged a battery of newly invented Leyden jars into the poor fellows (they are the first capacitors). All the monks reacted to the blow at the same time, and this made it clear that the speed of the current was extremely high.

Brilliant loser

Interesting facts from the lives of physicists can give false hope to unsuccessful students. There is a legend among careless students that the famous Einstein was a real bad student, knew little mathematics and generally failed his final exams. And nothing, it became worldwide. We hasten to disappoint: Albert Einstein began to show remarkable mathematical abilities as a child and had knowledge that far exceeded the school curriculum.

Perhaps rumors about the scientist’s poor performance arose because he did not immediately enter the Higher Polytechnic School of Zurich. Albert passed the exams in physics and mathematics brilliantly, but did not score the required number of points in other disciplines. Having improved his knowledge in the necessary subjects, the future scientist successfully passed the exams the following year. He was 17 years old.

Birds on a wire

Have you noticed that birds love to sit on wires? But why don’t they die from electric shock? The thing is that the body is not a very good conductor. The bird's feet create a parallel connection through which a small current flows. Electricity prefers wire, which is the best conductor. But as soon as the bird touches another element, for example, a grounded support, electricity rushes through its body, leading to death.

Hatches against cars

Interesting facts about physics can be remembered even while watching Formula 1 city races. Sports cars move at such high speeds that low pressure is created between the bottom of the car and the road surface, which is quite enough to lift the manhole cover into the air. This is exactly what happened at one of the city races. The manhole cover collided with the next car, causing a fire and the race was stopped. Since then, to avoid accidents, hatch covers have been welded to the rim.

Natural nuclear reactor

One of the most serious branches of science is nuclear physics. There are interesting facts here too. Did you know that 2 billion years ago there was a real natural nuclear reactor operating in the Oklo area? The reaction continued for 100,000 years until the uranium vein was exhausted.

An interesting fact is that the reactor was self-regulating - water entered the vein, which played the role of a neuron inhibitor. When the chain reaction was active, the water boiled away and the reaction weakened.

Hello, dear readers.

In the “Playing Physics” project there is a season of games and acquaintance with the concept. The first review of experiments from the Internet was dedicated. And today we’ll see what experiments they do with water pressure and how they play with it.

The first thing I found was an article about pressure on the Cool Physics website. There are many interesting puzzles - questions about fluid pressure. And the experience in the picture is very revealing and interesting, it seems to me. It is immediately visible and clearly shown that at different depths, the fluid pressure is different.

At school (or at the institute?) We deduced Bernoulli’s law for a long time using formulas. As a result, no one remembered the meaning. Me too. But it turns out that everything is, in principle, simple. But it's paradoxical. And this is especially interesting for both adults and children). The photo shows an experiment with air according to this law, or it can be done with water.

I came across an interesting game. It is, but of course it's not for kids. But it should be very interesting for schoolchildren to play like this.

And here is a video demonstrating the physical law. Almost a cartoon)

You can experiment with Pascal's ball. In principle, this is an ordinary sprinkler. And what kind of scientific instrument turns out to be) We at school simply squealed when this experiment was demonstrated. Although, it seems, it was already the ninth grade)

The experiment with communicating vessels is very interesting. I always thought that this topic was very simple and boring. Ah, no. There are quite a lot of interesting and important moments in it.

If you think physics is a boring and unnecessary subject, then you are deeply mistaken. Our entertaining physics will tell you why a bird sitting on a power line does not die from electric shock, and a person caught in quicksand cannot drown in it. You will find out whether there really are no two identical snowflakes in nature and whether Einstein was a poor student at school.

10 interesting facts from the world of physics

Now we will answer questions that concern many people.

Why does a train driver back up before moving off?

This is all due to the force of static friction, under the influence of which the train cars are standing motionless. If the locomotive simply moves forward, it may not move the train. Therefore, it slightly pushes them back, reducing the static friction force to zero, and then accelerates them, but in a different direction.

Are there identical snowflakes?

Most sources claim that there are no identical snowflakes in nature, since their formation is influenced by several factors at once: humidity and air temperature, as well as the trajectory of the snow. However, interesting physics says: it is possible to create two snowflakes of the same configuration.

This was experimentally confirmed by researcher Karl Libbrecht. Having created absolutely identical conditions in the laboratory, he obtained two externally identical snow crystals. True, it should be noted: their crystal lattice was still different.

Where in the Solar System are the largest reserves of water?

You'll never guess! The largest reservoir of water resources in our system is the Sun. The water there is in the form of steam. Its highest concentration is found in places we call “sunspots.” Scientists even calculated: in these areas the temperature is one and a half thousand degrees lower than in other areas of our hot star.

What invention of Pythagoras was created to combat alcoholism?

According to legend, Pythagoras, in order to limit the consumption of wine, made a mug that could be filled with an intoxicating drink only to a certain level. As soon as you exceeded the norm by even a drop, the entire contents of the mug flowed out. This invention is based on the law of communicating vessels. The curved channel in the center of the mug does not allow it to be filled to the brim, “riding” the container of all contents when the liquid level is above the bend of the channel.

Is it possible to turn water from a conductor into a dielectric?

Interesting physics says: it’s possible. Current conductors are not the water molecules themselves, but the salts contained in it, or rather their ions. If they are removed, the liquid will lose its ability to conduct electricity and become an insulator. In other words, distilled water is a dielectric.

How to survive a falling elevator?

Many people think that you need to jump when the cabin hits the ground. However, this opinion is incorrect, since it is impossible to predict when the landing will occur. Therefore, entertaining physics gives another advice: lie with your back on the floor of the elevator, trying to maximize the area of ​​​​contact with it. In this case, the force of the impact will not be directed to one area of ​​the body, but will be evenly distributed over the entire surface - this will significantly increase your chances of survival.

Why doesn't a bird sitting on a high voltage wire die from electric shock?

Birds' bodies do not conduct electricity well. By touching the wire with its paws, the bird creates a parallel connection, but since it is not the best conductor, charged particles do not move through it, but along the cable conductors. But if the bird comes into contact with a grounded object, it will die.

The mountains are closer to the heat source than the plains, but at their peaks it is much colder. Why?

This phenomenon has a very simple explanation. The transparent atmosphere allows the sun's rays to pass through without hindrance, without absorbing their energy. But the soil absorbs heat well. It is from this that the air then warms up. Moreover, the higher its density, the better it retains the thermal energy received from the earth. But high in the mountains the atmosphere becomes rarefied, and therefore less heat is retained in it.

Can quicksand suck you in?

There are often scenes in films where people “drown” in quicksand. In real life, says entertaining physics, this is impossible. You won’t be able to get out of a sandy swamp on your own, because to pull out just one leg, you’ll have to put in as much effort as it takes to lift a medium-weight passenger car. But you won’t be able to drown either, since you’re dealing with a non-Newtonian fluid.

Rescuers advise in such cases not to make sudden movements, lie down with your back down, spread your arms to the sides and wait for help.

Does nothing exist in nature, watch the video:

Amazing incidents from the lives of famous physicists

Outstanding scientists are mostly fanatics of their field, capable of anything for the sake of science. For example, Isaac Newton, trying to explain the mechanism of perception of light by the human eye, was not afraid to experiment on himself. He inserted a thin ivory probe into the eye while pressing on the back of the eyeball. As a result, the scientist saw rainbow circles in front of him and thus proved: the world we see is nothing more than the result of light pressure on the retina.

Russian physicist Vasily Petrov, who lived in the early 19th century and studied electricity, cut off the top layer of skin on his fingers to increase their sensitivity. At that time, there were no ammeters and voltmeters that made it possible to measure the strength and power of current, and the scientist had to do this by touch.

The reporter asked A. Einstein whether he writes down his great thoughts, and if he writes them down, where - in a notebook, a notebook or a special card index. Einstein looked at the reporter’s voluminous notebook and said: “My dear! Real thoughts come to mind so rarely that it is not difficult to remember them.”

But the Frenchman Jean-Antoine Nollet preferred to experiment on others. Conducting an experiment in the mid-18th century to calculate the speed of transmission of electric current, he connected 200 monks with metal wires and passed voltage through them. All participants in the experiment twitched almost simultaneously, and Nolle concluded: the current runs through the wires very, very quickly.

Almost every schoolchild knows the story that the great Einstein was a poor student in his childhood. However, in fact, Albert studied very well, and his knowledge of mathematics was much deeper than what the school curriculum required.

When the young talent tried to enter the Higher Polytechnic School, he scored the highest score in the core subjects - mathematics and physics, but in other disciplines he had a slight deficiency. On this basis he was refused admission. The next year, Albert showed excellent results in all subjects, and at the age of 17 he became a student.

Take it for yourself and tell your friends!

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